Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines...Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.展开更多
本试验从细管规格、基础稀释液成分(柠檬酸和甘氨酸)、甘油浓度和解冻方法对猪精液在-80℃超低温冰箱中冷冻保存冻后精子存活率的影响进行了研究。结果表明:(1)0.25 m L和0.5 m L细管之间没有明显差异(P>0.05),其冻后存活率均达到0.5...本试验从细管规格、基础稀释液成分(柠檬酸和甘氨酸)、甘油浓度和解冻方法对猪精液在-80℃超低温冰箱中冷冻保存冻后精子存活率的影响进行了研究。结果表明:(1)0.25 m L和0.5 m L细管之间没有明显差异(P>0.05),其冻后存活率均达到0.57左右。(2)冷冻液中甘油浓度为3%时,冻后猪精子存活率最高,达0.50±0.035;基础液中柠檬酸的含量为1.3%时,精子的冻后存活率极显著高于1.7%时(P<0.01);基础液中甘氨酸的含量为7.5 mg/m L时,则不能影响精子的冻后存活率(P>0.05)。(3)解冻方法为61℃5 s时,精子冻后存活率最高,达0.61±0.055。展开更多
文摘Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.
文摘本试验从细管规格、基础稀释液成分(柠檬酸和甘氨酸)、甘油浓度和解冻方法对猪精液在-80℃超低温冰箱中冷冻保存冻后精子存活率的影响进行了研究。结果表明:(1)0.25 m L和0.5 m L细管之间没有明显差异(P>0.05),其冻后存活率均达到0.57左右。(2)冷冻液中甘油浓度为3%时,冻后猪精子存活率最高,达0.50±0.035;基础液中柠檬酸的含量为1.3%时,精子的冻后存活率极显著高于1.7%时(P<0.01);基础液中甘氨酸的含量为7.5 mg/m L时,则不能影响精子的冻后存活率(P>0.05)。(3)解冻方法为61℃5 s时,精子冻后存活率最高,达0.61±0.055。
